The present invention relates generally to improvements in methods of producing molten iron. More particularly, the invention concerns a method for stabilizing the operation of a post-combustion smelting process for producing hot, molten iron from iron ores and/or other iron-bearing oxides. The Government of the United States of America has rights in this invention pursuant to Cooperative Agreement No. DE-FC07-94ID13284, awarded by the U.S. Department of Energy.
Methods of producing iron by smelting reduction, utilizing post-combustion technology with iron ore and coal-based fuels, are well known in the art. In such processes, it is preferable to use process controls that maintain a stable smelting operation, while maximizing the molten iron production rate. In addition, it is preferable to simultaneously minimize the fuel and oxygen consumption rates. However, in direct ironmaking processes there are numerous operating parameters that affect both the rate of iron production and the rate of fuel consumption. Moreover, these same parameters generally affect the quality of the molten iron produced. Within the smelter reactor, the material feed rates, the oxygen flow rate, the bottom stirring gas flow rate, the oxygen lance and tuyere configuration, the oxygen lance height, the system pressure, and the slag weight are all examples of variables that generally affect the operating performance of the smelter reactor.
Prior art process control methods can fail to effectively maintain control of the molten iron temperature and/or the chemical composition of the hot metal produced. Moreover, prior methods of control can cause the slag to foam out of the smelter reactor. It is an object of the present invention to design a method for the stable operation of a smelter reactor that overcomes one or more of those deficiencies of the prior art.